This section provides background information related to the present disclosure which is not necessarily prior art.
Hydraulic tensioners are used for applying tension against a chain or belt for preventing chain rattle or belt slippage in an auxiliary drive system of an engine or in other industrial machines. In a typical hydraulic tensioner as illustrated in FIG. 4a, a cylindrical plunger 100 is disposed within a cylindrical bore 102 of a housing and is biased against a tensioner shoe for applying a tension force against a belt or chain. A high pressure oil is introduced into the bore 102 for damping movement of the plunger. The oil is forced from the high-pressure chamber where it passes through a clearance 104 around the plunger 100 and into the chain cavity. Typically, to create high amounts of damping without high damping force, a hydraulic tensioner requires a larger clearance between the plunger and the bore. The high clearance makes it difficult to keep the plunger concentric with the bore during operation, which makes it prone to binding or stiction (tendency to bind or stick due to friction). With a limited clearance 104 due to the requirement of concentricity between the plunger 100 and bore 102, the force verses plunger displacement curve as shown in FIG. 4b has a limited damping capability. Accordingly, it is desirable to provide a tension device with improved damping while maintaining concentricity between the plunger and the bore.
According to the present disclosure, a hydraulic chain or belt tensioner is provided with a plunger having a non-round profile within the cylindrical bore allowing for concentric position of the plunger relative to the bore that can be minimized, while the effective hydraulic clearance can be increased to provide higher damping with less damping force.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.